Latest News


‘Safety Contactors’ defined

Do Schneider Electric offer ‘safety contactors’?

A question we are frequently asked is do Schneider Electric offer a ‘safety’ contactor?

The answer to this is that the term ‘safety contactor’ does not appear to have any clear definition within the Safety of Machinery standard IEC (BS EN) 60204-1 or within IEC (BS EN) 60947-4-1, the standard associated with contactors. Since there does not appear to be any clear definition of what is required from a ‘safety contactor’ we cannot confirm if there is such a product in the range. However, Schneider Electric does have contactor products with ‘mirror contacts’ that can be used to switch off the supply to a motor as part of a machine safety system.

Mirror Contacts

Mirror contacts are defined within IEC (BS EN) 60947-4-1. The essence of the mirror contact function (refer to the standard for a full explanation) states that the N/C auxiliary contact on each contactor will not close when one of the power contacts is closed and can therefore be connected to a safety monitoring relay, such as a Preventa relay. Schneider Electric’s TeSys D contactors and TeSys U combined contactor circuit breaker ranges incorporate N/C mirror contacts in accordance with IEC (BS EN) 60947-4-1.

Mechanically linked or guided contacts

It is worth mentioning that prior to the introduction of mirror contact terminology, the requirement for reliable signaling from a N/C contactor auxiliary has, in some instances, been referred to as mechanically linked or guided contacts. Using this terminology to describe the requirements of a contactor can be misleading, as the definition of a mechanically linked or guided contact is the non-overlap of all N/O and N/C contacts. This terminology was originally used with respect to relays used in a variety of applications including railway signal interlocking. To claim this feature for a contactor without clarification is unwise as it implies that the condition of a very small auxiliary contact can influence the status of a potentially very large power contact controlled by a powerful electromagnet. Thus the introduction of the mirror contact specification that only considers the influence of the power contacts on the auxiliary and not the auxiliary on the power contacts.

Clearly visible safety chain makes your life easier

Clear visability on standard TeSys range
Clear visability on standard TeSys range

Schneider Electric’s range of TeSys contactors and TeSys U motor starters are certified according to IEC 60947-4-1 for safety applications thanks to the integrated mirror contact. Therefore a standard Schneider contactor may be used in safety applications (giving you a substantial cost saving) whereas other manufacturers have a specific ‘safety’ contactor in the range as their standard contactors will not suffice. To help with identification of contactors in safety applications, Schneider have produced a range of retrofit contactor safety covers which are Red in colour, in addition to this an auxiliary contact block 2 N/O + 2 N/C is also available with a Red face plate. For further information on this safety-chain identification system please click the download button below.

For further information on contactors for safety applications, please do not hesitate to contact us

Download

Newsletter Signup

Sign up for the latest news from AJ Hurst